Many diabetics suffer from severe cardiomyopathy even in the absence of vascular disease. Evidence from animal models and clinical samples implicate reactive oxygen species (ROS) in the development of diabetic cardiomyopathy. Our results confirm the importance of ROS. In the OVE26 model of Type I diabetes we find increased cardiac oxidative damage, increased production of ROS by diabetic cardiomyocytes and protection by antioxidant transgenes. Two different antioxidant proteins targeted to the cardiomyocyte, metallothionein (MT) and catalase prevented most of the primary characteristics of diabetic cardiomyopathy, including reduced contractility, impaired calcium homeostasis and disrupted morphology. Our most recent data implicate mitochondrial electron transport and the enzyme NADPH oxidase in the production of oxidative damage in diabetic cardiomyocytes. This project will identify the cellular source of increased ROS production in diabetic hearts, determine which proteins are the targets of ROS modification and test whether the importance of ROS in Type I diabetes also applies to cardiomyopathy in Type II diabetes. Sources of ROS will be tested by measuring ROS production in diabetic cardiomyocytes as a function of genetic knockout or drug inhibition of potential sources. Breeding diabetic mice to knockout mice for NADPH oxidase will determine if this enzyme is required for the development of diabetic cardiomyopathy. Protein targets of ROS modification in whole heart, mitochondria and sarcoplasmic reticulum will be identified by using proteomic analysis combined with antibodies against oxidatively modified amino acids. To analyze the role of ROS in Type II diabetic cardiomyopathy we will characterize cardiac morphology, ROS production, cardiac function and oxidative damage in the agouti model of Type II diabetes. Agouti mice will be bred to mice protected by cardiac specific antioxidant transgenes to determine if oxidative damage is a requirement for cardiomyopathy in this model.